1. Field of the Invention
The invention relates generally to the field of instruments conveyed into subsurface wellbores by armored electrical cable. More specifically, the invention relates to devices for moving such instruments to a selected rotary orientation within a wellbore.
2. Background Art
Many types of instruments are used in wellbores drilled through subsurface rock formations. Such instruments can include, among other devices, sensors for measuring properties of the rock formations outside the wellbore, energy sources for various types of surveying or evaluation, mechanical wellbore intervention tools and directional survey instruments, as non limiting examples. Such instruments may be conveyed along the inside of the wellbore by a technique generally known as “wireline” in which an armored cable having one or more insulated electrical conductors therein is extended into and withdrawn from the wellbore using a winch, and in which the instruments are disposed at the end of the cable.
In some cases, it may be desirable to move the instrument to a selected rotary orientation within the wellbore. Such orientations may include having sensors on the instrument directed toward, for example, the gravitationally upwardmost direction (“high side”) for purposes of surveying the trajectory of the wellbore. Other examples may include having a seismic energy source oriented in the direction of an adjacent wellbore.
Irrespective of the reason for requiring rotary orientation capability, it has proven impractical to provide such capability when instruments are conveyed into a wellbore by wireline.